I mean, a unique digital fingerprint can be created by the links that your device makes with other devices without you having any input at all

I think the point here with the patent is the number of photos that the user takes with other users... then you enter in the circle of verified people, this is difficult to cheat by a bot/IA I think (at least today 2019).
Then, in this sense they can introduce "one account one vote" in Voice without taking into account the stake.

Oh yeah, and what happnes when you lose your device? Not sure.

I suppose that you can recover your account with other device. Just take again more pictures of you and claim that you are the real one. As the old device can not create proofs (pictures of you) then the blockchain can update your device id.